With the expanding use of the Internet and mobile communications, carrier networks provided by communications firms are shifting from time division multiplexing (TDM) network, such as Synchronous Optical NETwork/Synchronous Digital Hierarch (SONET/SDH), to packet networks utilizing the Ethernet (registered trademark) technique and the Internet protocol (IP) technique. In the packet networks including wide-area Ethernet service, a mobile network, and so on, a frame transfer process is performed by learning a media access control (MAC) address of a frame.
In a communication device such as a frame transfer device, the learning of the MAC address is realized by registering, in a MAC address table, a transmission source MAC address of a received frame and input port information of the received frame. The input port information includes, for example, a card number identifying an interface card, and a port number identifying a physical communication port. In the frame transfer device, for example, when a frame arrives at some one physical communication port of some one interface card, the card number identifying the relevant interface card and the port number identifying the relevant physical communication port are registered in the MAC address table together with the transmission source MAC address of the received frame.
The frame transfer device transfers the received frame by employing the above-mentioned MAC address table. In more detail, the frame transfer device searches the MAC address table using a destination MAC address of the received frame, thereby specifying a card number and a port number corresponding to the destination. The frame transfer device then transmits the frame via the specified communication port of the specified interface card.
When the destination MAC address of the received frame is not yet learned (i.e., when the destination MAC address of the received frame is not registered in the MAC address table), the frame transfer device transfers the relevant frame via all the communication ports by broadcasting. Such broadcast transfer is often called “flooding”.
For example, Japanese Laid-open Patent Publication No. 2010-114724, IEEE Std 802.1D-2004, and so on are disclosed as related art.
In the learning of the MAC address according to the related art, when a new MAC address is detected, the new MAC address is simply registered in a blank entry of the MAC address table. Therefore, for example, when the learning is performed on a large amount of MAC addresses regarding a particular user, many entries of the MAC address table are occupied by the particular user, and the learning of the MAC address regarding other users is not performed. In such a case, a great deal of flooding is generated for traffics related to the other users, and a network is congested. Thus, according to the related art, network resources (herein, entries of the MAC address table) may not be equally allocated to individual users.
The above-described problem is not concerned only with the learning of the MAC address, and it may occur in a communication device storing, in a memory, information for controlling a frame transfer destination.